Earth's climate for the last 2.5 million years has been characterized by the waxing and waning of large continental ice sheets in the Northern Hemisphere. Prior to 1.2 million years ago, the glacial-interglacial cycles marched to the beat of the tilt of Earth's rotational axis (i.e., obliquity), which varied with a cycle of 41,000 years. About a million years ago, the length of glacial-interglacial cycles became longer, averaging about 100,000 years. The 100-kyr world is notoriously difficult to understand because of the highly non-linear response of climate to insolation forcing. This project is focused on the 41-kyr world that is thought to represent a more linear response of ice sheets and climate to orbital forcing via integrated summer insolation.

Project summary:

The glacial-interglacial cycles of the 41-kyr are more symmetric than those of the sawtooth structure of the late Pleistocene; however, they are not perfectly symmetrical. The unique cycle shapes are related to the varying influences of precession and obliquity to the integrated summer insolation. Changes in the waveform of the d18O cycles can be exploited to constrain the nature of the forcing. This represents a new method that takes advantage of the shape of isotope signals to constrain the forcing of glacial-interglacial climate in the 41-kyr world and provide additional stratigraphic opportunities for correlating oxygen isotope records to insolation forcing. The project has the potential to significantly increase our understanding of the great Ice Ages.

What the student will do:

The student will produce high-resolution stable isotope measurements of benthic and planktic foraminifera during the 41-kyr world at several key ODP/IODP sites. Trace element data (Mg/Ca) will be used to deconvolve the temperature and water isotope (ice volume) components of the d18O signal. Statistical methods will be to used to analyze the waveform of the isotope signals and compare them with orbital targets.

Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.

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